drm/omap: fix compile error when DPI is disabled

When CONFIG_OMAP2_DSS_DPI is disabled, compilation fails due to:

drivers/gpu/drm/omapdrm/dss/dss.h:388:25: error: conflicting types for ‘port’
     struct device_node *port,
                         ^~~~

Fix this by renaming the first parameter correctly.
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

drivers/gpu/drm/omapdrm/dss/dss.h

@@ -383,7 +383,7 @@ int dpi_init_port(struct dss_device *dss, struct platform_device *pdev,
 		  struct device_node *port, enum dss_model dss_model);
 void dpi_uninit_port(struct device_node *port);
 #else
-static inline int dpi_init_port(struct dss_device *port,
+static inline int dpi_init_port(struct dss_device *dss,
 				struct platform_device *pdev,
 				struct device_node *port,
 				enum dss_model dss_model)